The present invention relates to an improvement in the frequency-position characteristic of electronic wrist watches by improving the frequency temperature characteristic of the time standard signal using a plurality of piezoelectric vibrators, for instance, two piezoelectric vibrators.
Conventionally, a method for connecting two piezoelectric vibrators in parallel is shown in FIG. 1 to obtain a frequency-temperature characteristic as shown in FIG. 2 has already been proposed. However, in a portable instrument such as an electronic wrist watch, the main problem to be solved is to decrease the frequency-position characteristic in order to use a vibrator of this type for the standard signal of the portable instrument, since the frequency-position characteristic is an important element in a portable instrument such as the electronic wrist watch. Particularly, in order to make a highly precise electronic wrist watch, the frequency-position and frequency-temperature characteristics should be held down to within several tenths P.P.M., and thus a method to hold the frequency-position characteristic within the above value is strongly desired.